Exhaust cap apparatus



July 8, 1969 A. s. LUNDY EXHAUST CAP APPARATUS Filed Sept. 11, 1967 INVENTOR; ALVIN s. LUN DY ATT'YS United States Patent 3,453,946 EXHAUST CAP APPARATUS Alvin S. Lundy, Bloomfield Hills, Mich., assignor to Claude B. Schneible Co., Holly, Mich., a corporation of Michigan Filed Sept. 11, 1967, Ser. No. 666,590 Int. Cl. F23] 17/12; F23 11/02 US. Cl. 98--58 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to an exhaust cap apparatus for use with gas-flow apparatus, and more particularly, for use with a foundry cupola stack. The top of the stack may or may not be equipped with a primary collecting device such as described in United States Patent Nos. 2,597,192 and 2,643,867.

In order to decrease air pollution many foundries now use dust collecting systems in conjunction with their cupolas or other melting structures. The gas collecting systems withdraw the products of combustion and induced air entering through charging opening from the cupola during normal operation, remove the particulate matter and perhaps also gaseous pollutants from the gases, and discharge the purified gas to the atmosphere. However, in the event of a power breakdown or other failure of the collecting system, emergency discharge means must be provided for bypassing the dust collecting system in order to protect the expensive equipment and to remove the noxious fumes, dust, etc. from the foundry. Those cupolas having their connection to the collecting system. above the charging opening are provided with a closed top, and in the past an emergency discharge opening has been provided by a removable counterweighted cover on the top of the cupola stack or primary collecting device. The cover is held closed during normal operation by an air cylinder or the like, and in the event of collecting system failure the air cylinder operates to release the counterweights and open the cover. This and other types of emergency discharge rneans have proved both cumbersome and expensive, and are likewise subject to failure.

SUMMARY OF THE INVENTION My exhaust cap assembly provides a simple and inexpensive emergency discharge bypass of the dust collecting system. The apparatus has no moving parts which require servicing or repair, and there is relatively little if any chance that the apparatus will fail to perform its intended function in the event of a breakdown of the dust collecting system.

DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of the apparatus embodying my invention; and FIG. 2 is a sectional view taken along the line 22 of FIG. 1.

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DESCRIPTION OF THE PREFERRED EMBODIMENT -In the illustration given, the numeral 10 designates a cylindrical conduit such as a cupola stack or other gasfiow column provided with a refractory lining 11 and an open end 12. The cupola is of well known construction and need not be described in detail. Mounted above the top of the stack or column is a generally cylindrical exhaust cap 13 provided with a closed upper end 14 and an exhaust opening 15. Exhaust duct 16 extends radially outwardly from the exhaust opening and is joined to duct 17 by frusto-conical connector duct 17a. Duct 17 in turn is connected to a conventional dust collecting system (not shown). The dust collecting system may take the form of any of a number of well known systems, such as those shown in Patent Nos. 2,197,595 and 2,696,105.

The exhaust cap 13 is secured to the top of the stack 10 and spaced therefrom by generally upwardly extending support bars 18 which are circumferen'tially spaced about the exhaust cap and stack and suitably secured thereto as by welding. Although four support bars 18 are illustrated, it is to be understood that more or less bars may be used depending upon the size of the stack and exhaust cap. The spaced-apart relationship between the exhaust cap 13 and the stack 10 provides a plurality of emergency exhaust openings 19 between adjacent support bars 18. In the preferred embodiment the inside diameter of exhaust cap 13 is slightly greater than the inside diameter of stack 10 so that upwardly flowing gases from the stack may be slightly divergent and still be captured by the exhaust cap. In the illustration given, the support bars 18 diverge outwardly slightly to accommodate the wider exhaust cap.

A frusto-conical windshield 20 is disposed about the emergency exhaust openings 19 with its wide end 21 disposed upwardly. The windshield 20 is secured to the top of stack 10 by a plurality of circumferentially spaced brackets 22, and the narrow end 23 of the windshield is advantageously spaced from the stack 10 so that particulate material is not accumulated between the windshield and the stack.

OPERATION During normal operation the stack gases flow upward- 1y through the stack '10 in the direction indicated by the upwardly extending solid arrows and are collected by the exhaust cap 13. The gases are withdrawn from the exhaust cap through exhaust opening 15 and exhaust duct 17 under the influence of the forced draft or suction created by the dust collecting system. For purposes of illustration, the forced draft created by the dust collecting system is represented schematically by the fan F shown in dotted outline. 'Ihe gases pass into the dust collecting system where the dust and other particulate matter and pollutants are removed, and the purified gas is discharged into the atmosphere. The forced draft created by the dust collecting system draws the gas upwardly from the stack 10 past the emergency discharge openings 19 and into the exhaust cap 13. Even if the gases diverge slightly outwardly as they pass from the stack 10, the somewhat wider exhaust cap 13 will capture the gases.

The windshield 20 prevents wind from blowing the stack gases away from the exhaust cap. As can be seen in FIG. 2, the top of the windshield extends above the bottom of the exhaust cap, and the bottom of the wind shield extends below the top of the stack to provide effective shielding for the openings 19.

In the event of a failure of some component of the dust collecting system so that a forced draft is not available, the stack gases will automatically bypass the exhaust cap 13 and flow through the emergency discharge 3 openings 19 and over the top of the windshield 20 into the atmosphere, as indicated by the arrows in dotted outline. In the illustration given the relatively narrow support bars 18 are spaced 90 apart, and the gases may pass outwardly through the openings 19 substantially throughout a full 360".

The narrow end 23 of the windshield 20 is spaced from the outer surface of the stack so that any particulate matter that falls out of the gas stream during emergency operation will not accumulate between the windshield and the stack. As indicated in FIG. 2, the particulates designated P pass through the space between the windshield and the stack.

In normal operation the gas flow of the stack may vary considerably depending upon a number of factors. For example, an unusually large amount of air may enter the stack through the charging opening, and the gas volume flowing up the stack may be much greater than anticipated. Since the dust collecting system is normally set to accommodate the products of combustion plus maintaining a certain average velocity of air through the charging opening, the stack gas volume might at times exceed by an appreciable amount the capacity of the collecting system. In such a case, considerable gas might bypass the exhaust cap 13 and flow through the emergency discharge openings 19 even during normal operation. Since the emergency discharge openings are intended for use only when the dust collecting system fails, it is desirable to provide some control on the volume of gas flowing through the stack. I have found that it is advantageous to provide the top of the stack 10 with a discharge restriction ring 25 which has an inside diameter less than the inside diameter of the cupola stack. In the illustration given, the discharge restriction ring 25 is segmented, having arcuate portions 25a, 25b, 25c, and 25d. In most instances, however, the discharge restriction ring 25 would not be installed until after the need for it in a particular cupola is demonstrated.

Since the stack gases may be as hot as 2,000 F. or more, I have found it advantageous to construct the various parts of my apparatus of heat resistant materials.

While I have described my exhaust cap apparatus in conjunction with a cupola stack, it may also be used on other devices such as, for example, primary collector devices such as described in United States Patent Nos. 2,597,192 and 2,643,867. The apparatus might also be used on a horizontal run of duct or breeching.

While in the foregoing specification, I have set forth a specific structure in considerable detail for the purpose of illustrating an embodiment of the invention, it is to be understood that many of the details herein given may be varied considerably by those skilled in the art without departing from the spirit and scope of my invention.

I claim:

1. In a gas-flow apparatus including a gas-flow conduit, an exhaust cap mounted on the end of said conduit in spaced relation therewith, said exhaust cap being provided with an exhaust opening adapted to communicate with draft-providing means whereby gas normally flows through said conduit into said exhaust cap and through said exhaust opening, a windshield mounted on said conduit and disposed about the space between said column and said exhaust cap, one end of said Windshield extending 4 beyond the end of said exhaust cap adjacent the conduit and the other end of said windshield extending beyond the end of said conduit whereby normal gas flow from said conduit to said exhaust cap is substantially unaffected by Wind, said windshield being spaced from said exhaust cap to provide an emergency gas flow passage therebetween in the event of failure of the draft-providing means.

2. In a gas-flow apparatus including an upwardly extending generally cylindrical gas-flow column, a generally cylindrical exhaust cap provided with a closed upper end and an exhaust opening, said exhaust cap being mounted on the top of said column in spaced relation therewith by a plurality of circumferentially spaced cap support bars, an exhaust duet secured to said exhaust cap about said exhaust opening, said exhaust duct being adapted to communicate with draft-providing means whereby gas normally flows upwardly from said colum into said exhaust cap and through said exhaust duct, a windshield mounted on said column and circumferentially disposed about the space between said column and said exhaust cap, said windshield extending upwardly from below the top of said column to above the bottom of said exhaust cap whereby normal gas flow from said column to said exhaust cap is substantially unaffected by wind, the upper portion of said windshield being spaced radially outwardly from said exhaust cap to provide an emergency gas flow passage between said windshield and said exhaust cap in the event of failure of the draft-providing means.

3. The structure of claim 2 in which said windshield is generally frusto-conical and diverges upwardly and outwardly, the lower end of said windshield being spaced outwardly from said column.

4. In a gas-flow apparatus including an upwardly extending gas-flow column, an exhaust cap mounted on the top of said column in spaced relation therewith, said exhaust cap being provided with an exhaust opening adapted to communicate with draft-providing means whereby gas normally flows upwardly from said column into said exhaust cap and through said exhaust opening, a generally frusto-conical windshield mounted on said column and disposed about the space between said column and said exhaust cap, said windshield extending from below the top of said column and diverging outwardly and upwardly to above the bottom of said exhaust cap whereby normal gas flow from said column to said exhaust cap is substantially unafiected by wind, said windshield diverging outwardly beyond said exhaust cap to provide an emergency gas flow passage therebetween in the event of failure of the draft-providing means.

References Cited UNITED STATES PATENTS 198,350 12/1877 Chase 9884 3,049,113 8/1962 Northwood et a1. 126-307 XR 3,209,670 10/1965 Twickler 9884 3,307,470 4/1967 Kenny et al. 98--58 FRED C. MATTERN, 111., Primary Examiner.

MANUEL ANTONAKAS, Assistant Examiner.

US. Cl. X.R. 126-307 

